Localization of adenosine receptor messenger RNAs in the rat eye

Adenosine is present in all cells and body fluids and has been suggested to play several roles in the physiology of ocular tissues. The present study was undertaken to determine which types of adenosine receptor mRNAs are present in the rat eye, and where they are expressed. RNA or deoxyoligodeoxynucleotides complementary to rat adenosine receptor subtypes A(1), A(2A), A(2B) and A(3) were used to generate S-35 labeled antisense and sense probes. The probes were then used for in situ hybridization on 10 mu m cryosections of the rat eye including the cornea, iris, ciliary body, lens, retina, choroid and sclera. A(1), A(2A) and A(2B) receptor mRNAs were demonstrated in the ciliary processes. A(1) receptor mRNA was also expressed in the ganglion cell layer of the retina. The retina also showed A(2A) receptor mRNA expression, which was most prominent in the inner nuclear layer and less prominent in the ganglion cell layer and outer nuclear layer. Weak A(2A) expression was found in the retinal pigment epithelium and choriocapillaris. No significant expression of A(3) receptor mRNA was found in the rat eye. In conclusion, using in situ hybridization, we have demonstrated expression of mRNA for A(1), A(2A) and A(2B) adenosine receptors in the rat eye. The expression patterns support specific roles for adenosine in the ciliary process and retina. (C) 1997 Academic Press Limited.